ENERGY SELF SUFFICIENCY WITH RENEWABLE SOURCES BIOMASS AND WIND IN THE REHABILITATION PROJECTOF AN OLD RURAL BUILDING COMPLEX IN SICILY (ITALY) Paola Caputo paola.caputo@polimi.it Politecnico di Milano, BEST Dep. Via Garofalo, 39 20133 Milano -Italy Abstract. BEST Dept. has been involved with Regione Sicilia in a research work of the UE MéRITE program for the development of integrated territorial management experiences in pilot areas. Main project goal was to design appropriate retrofit solutions and technologic systems for the rehabilitation of an old rural building complex in Sicily (Italy), reaching the energy self sufficiency with renewable sources. The first phase of the research included: Analysis and interpretation of wall materials and layers of the buildings Hypothesis of interventions for rehabilitation and improvement of the envelope thermalphysic characteristics Shape and volume study, equivalent volumes calculation and zones definition Detailed weather and climatic conditions evaluation and elaboration Building energetic behaviour simulation (with TRNSYS model) Energetic needs evaluation for electricity, heating and cooling Preliminary plant design for power generation or heat and power cogeneration Comparison of solutions as energy sources Basic benefits and cost evaluation of each solutions. In the second phase, on the base of the available renewable energy sources (wood biomass from the near forests, sun, wind and underground water), scenario wind turbines for electricity and biomass combustion for heating has been investigated in depth. Keywords: Renewable energy, Rehabilitation project, Wind turbine, Biomass 1. INTRODUCTION The present case study is related to rehabilitation of an old rural building complex (named Baglio ), located at Monti Sicani (in the centre of Sicily, between Palermo and Agrigento). Main objective is the designing of appropriate retrofit solutions and technological systems with the goal of reaching the energy self sufficiency with renewable sources.
Main steps of the project are: weather data elaboration, energy potential evaluation, energy analysis of buildings, identification and comparison of energy systems alternatives, analysis of the alternative electricity by grid-connected wind turbine and heat by wood combustion. For dealing in depth these subjects, please see [Butera and Caputo, 2004]. 2. ELABORATION OF THE METEOROLOGICAL DATA FILE After statistic elaborations reported in [Butera and Caputo, 2004] and fig. 1, monthly data adopted for site meteorological condition characterisation are: monthly mean temperature from trend curve Prizzi monthly mean relative humidity and Prizzi monthly mean beam and diffuse solar radiation. Due to the building conditions and to the aims of the project, a dynamic hourly model was used for the evaluation of buildings energy behaviour. To that end, Baglio site monthly mean data were used for calculating hourly data by means of a stochastic model by MeteoNorm program (see fig. 2 for hourly temperatures representation). Estimation of Baglio site monthly mean temperatures, C 30 25 20 15 10 prizzi mean monthly T C prizzi average monthly T, period 1959-1974 C lercara average monthly T, period 1958-1974 C 5 bivona average monthly T, period 1958-1974 C baglio Interpolation Prizzi-Lercara, results C baglio Interpolation Prizzi-Bivona, results C 0 baglio Trend Prizzi-Lercara-Bivona, results C jan feb mar apr may jun jul aug sep oct nov dec Figure 1. Monthly mean temperatures for the 3 stations considered and results of statistic evaluations for Baglio site temperature estimation 3 ENERGY ANALISYS OF THE BUILDING COMPLEX 3.1 Building description Besides an inspection, a set of documents, such as photographs, plans, diagrams, maps and surveys were considered, in order to define the characteristics of geometry and materials (state of conservation, composition, physical parameters) for the building complex (see fig. 3). Afterwards, thermal zones repartition were defined. Preliminary thermal classification was done referring to the expected use of each zone (for dimensional data see table 1).
Baglio hourly temperatures ( C) 40.00 35.00 30.00 25.00 20.00 15.00 10.00 5.00 0.00-5.00 1 300 599 898 1197 1496 1795 2094 2393 2692 2991 3290 3589 3888 4187 4486 4785 5084 5383 5682 5981 6280 6579 6878 7177 7476 7775 8074 8373 8672 Figure 2. MeteoNorm elaboration results; Baglio site hourly external temperatures 4 ENERGY ANALISYS OF THE BUILDING COMPLEX 4.1 Building description Besides an inspection, a set of documents, such as photographs, plans, diagrams, maps and surveys were considered, in order to define the characteristics of geometry and materials (state of conservation, composition, physical parameters) for the building complex (see fig. 3). Afterwards, thermal zones repartition were defined. Preliminary thermal classification was done referring to the expected use of each zone (for dimensional data see table 1). Table 1. Zones, surfaces and volumes Zone Preliminary Zone Expected use Surface Volume Surface, Volume, m 2 m 3 destination m 2 m 3 1 Technical zone 33.2 174.0 7 Reception 95.2 461.7 2 Naturalistic laboratories 94.4 495.3 8 Conference 189.4 1022.7 room 3 Visitor centre 107.1 358.8 9 Museum 141.1 712.6 4 WC 39.1 144.7 10 Offices 114.9 483.0 5 Classrooms 107.5 521.5 11 Guestroom 141.1 557.0 6 Exhibition room 268.1 1086.0 Sum 1331.1 6017.3 Based on the documentation collected and consideration for improving the energy characteristics (included in the aims of the project) respecting limitations of restoration and conservation project, next envelope U-values were defined: internal and external walls: between 1.42 and 0.56 W/m 2 K, depending on the thickness slab: 0.84 W/m 2 K floor slab: 0.40 W/m 2 K roof: 0.39 W/m 2 K double glass windows.
In order to carry out energetic simulations, internal loads (lighting [Butera, 1995], equipment and occupancy), temperature set points and schedules for lighting, equipment, occupancy and plants were assumed [Butera and Caputo, 2004]. 4.2 TRNSYS simulations Dynamic simulations were carried out implementing data (weather, geometry, thermal characteristics, internal loads and schedules) in TRNSYS in order to: determine energy demand and peak of heating, cooling and electricity evaluate alternative renewable energy systems choose the most suitable system taking into account available local resources and landscape and aesthetic problems. On the basis of the TRNSYS simulation results, such as hourly temperature for each thermal zone and hourly energy demand (heating and cooling) for each zone, the following parameters of building performance have been evaluated (fig. 4 and table 2). Figure 3: buildings description problem Table 2. Total heating and cooling demands and peaks Heating Cooling Electricity Energy demand; kwh/m 2 year 68 2 20 Peak power; kw 100 11 30
Energy demand in kwh (neg. values: heating; pos. values: cooling) Sep Aug Jul Jun May Apr Mar Feb Jan -5000.00 Dec Nov Oct 5000.00 0.00-10000.00-15000.00-20000.00-25000.00 Figure 4. Total thermal energy demand, monthly values 5 ENERGY SYSTEM ALTERNATIVES 5.1 Renewable energy sources Available renewable energy sources are sun, wind and wood biomass from the near forests. On the basis of these RE sources, five energy system alternatives have been defined and evaluated [Butera and Caputo, 2004] Economical and environmental pros and cons for each alternatives were evaluated. A summary is reported in table 3. The conclusion of the first phase was that best choice could integrate more than one alternative and will depend on overall project goals and social-economical-environmental effects and considerations. 5.2 Plant dimensions for preliminary design A summary of plant dimensions for preliminary design for each alternatives is reported in table 4. Plants and distribution systems will be integrated and managed by a smart multifunctional control system, with electrical loads priority list. 5.3 Environmental indicator Each wood combustion system described will meet the parameters about air pollution prescribed by law. In terms of CO 2 balance, referring to the Italian traditional conditions for electricity and heating generation, approximately 37 t/y of CO 2 emissions could be avoided (16 for electrical demand and 21 for heating demand) due to the energy self sufficiency with renewable sources technological systems.
Table 3. Summary of pros and cons of each energy supply Alternatives Pros Cons Notes Wood chips+miniwind Low cost Well established technologies Visual impact Wind speed not optimum (4-6 m/s) Nominal rotor performances with higher wind speed Wood chips+microwind Wood chips+pv Wood chips Stirling Wood pellets Stirling Wood chips (or other wood biomass) Seebeck effect Well established technologies Well established technologies Use of an abundant resource presently wasted No need for grid connection No visual impact Use of an abundant resource presently wasted No need for grid connection No visual impact Possible activation of new economic activities Use of an abundant resource presently wasted No need for grid connection No visual impact Need for grid connection Visual impact Wind speed not optimum (4-6 m/s) Need for grid connection High cost Visual impact for solar tiles architectural integration Need for grid connection Technology not yet mature Grid connection would be wise High cost Technology not yet mature Grid connection would be wise High cost Technology not yet mature Grid connection would be wise Need for heat sink Easier landscape integration for micro-rotors Higher Cost Nominal rotor performances with wind speed >10 m/s Need for wood biomass chain management and control Need for wood biomass chain management and control Benefits: start of pellet market Costs: need for wood treatment plant for pellet production Technical and economical feasibility only for oversize pellet production Electricity generation due to Seebeck effect with el / th = 1/10 Need for wood biomass chain management and control 5.4 Economical evaluation Indicative costs of main components for each alternatives are reported in fig 5. 6 WIND AND BIOMASS ALTERNATIVE Alternatives corresponding to low cost solutions have been considered. Because information about performance of wood chips Stirling engine has been not completed, solution corresponding to wood chips + wind has been evaluates. That means to evaluated a plant solution with use of biomass energy for heating and wind energy for electricity. In this case, grid connection is advised.
Table 4. Nominal powers for each alternative Alternatives Dimension Notes Wood chips+miniwind 2 x 55 kw th boilers 2 x 30 kw el wind turbines Wood chips+microwind 2 x 55 kw th boilers 25 x 3 kw el wind turbines Savonius - Darreus rotor type Wood chips+pv 2 x 55 kw th boilers Solar tiles roof integrated Pv captant surface = 160-170 m 2 Pv power = 20 kw p Wood chips Stirling 1 x 25 kw th boiler 1 x 35 kw el Stirling motor Back up: 1 x 35 kw el Stirling motor Wood pellets Stirling 1 x 25 kw th boiler 3 x 9 kw el Stirling motors Wood chips (or other wood biomass) Seebeck effect 1 x 30 kw el (300 kw th ) thermal plant with Seebeck effect Or 2 twin lines: 2 x 15 kw el (2 x 150 kw th ) costs for each plant alternative, k 350 300 250 200 150 100 50 0 wood chips+miniwind wood chips+microwind wood chips+pv wood chips Stirling wood pellets Stirling wood chips Seebeck Notes to figure 5: In general, not included: VAT (+), incentives (-), auxiliaries (+), assembly costs (+), heat and power distribution systems (+), control systems (+). For Wood chips Stirling : Danish experimental motor, actual cost not defined, 2 motor of 30 k/cad assumed Wood pellets Stirling: pellet production line (200 k) included; pellet market benefits not included Figure 5. Economical comparison: indicative costs of main components for each alternatives 6.1 Wind to electricity Before doing an anemometric campaign, wind data have been evaluated from Atlante Eolico dell Italia (elaborated by CESI and Università degli studi di Genova, ENERIT project [CESI, 2004]): mean wind velocity for the site is about 4-5 m/s at 25 m above ground level and 5-6 m/s at 50 m above ground level. Average wind turbine performance, for a standard dimension turbine, is about 2000-2500 MWh/MW. The European map for wind data elaborated by Risø National Laboratory gives the same wind parameters for the same zone of Sicily [http://www.windpower.org]. Wind turbine performance has been evaluated on the basis of wind turbine data base and calculators described by Danish Wind Industry Association [http://www.windpower.org], choosing a suitable wind turbine available in the market.
In the case corresponding to the best wind conditions, the energy output obtained using the wind power turbine calculator is about 25 MWh/y, that means the 97% of the electricity demand of the building complex. Table 5. Wind turbine performances, best case Mean velocity 5 m/s Rotor diameter 10.9 m Weibull shape parameter 1.37 Hub height 18 m Wind turbine nominal power 15 kw Max power input at 10 m/s Cut in speed 3 m/s Energy output 25357 kwh/y Cut out speed 25 m/s Capacity factor 19% In the case corresponding to the worst wind conditions, the energy output obtained using the wind power turbine calculator is about 9 MWh/y, that means the 35% of the electricity demand of the building complex. Table 6. Wind turbine performances, worst case Mean velocity 4 m/s Rotor diameter 10.9 m Weibull shape parameter 2 Hub height 18 m Wind turbine nominal power 15 kw Max power input at 10 m/s Cut in speed 3 m/s Energy output 9816 kwh/y Cut out speed 25 m/s Capacity factor 7% For the technical, environmental and economical decision about the best number of wind turbine to install, an anemometric campaign has to be carried out. Grid conditions, percentage of demand that has to be covered by wind power and grid interconnection conditions represent very important points for the final project definition. In order to give an overall evaluation of wind power generation for this case study, noise and shadow evaluations have been done, using calculators described by Danish Wind Industry Association [http://www.windpower.org]. Obtained results do not indicate significant impact on the landscape. 6.2 Biomass to heat The adoption of wood boilers has been designed in order to valorise the high quantity of wood waste from the surrounding forest, with a simple wood combustion system, without using particular wood-based fuel such as pellets. In this case, wood from forest will be treated to reach physical-chemical conditions suitable for the combustion process. After the preparation, wood boilers will ensure the casing of the heating demand and the attainment of the wanted thermal comfort conditions. Nowadays, wood combustion for domestic use represents a consolidate technology and there are many company in the market for boilers production and selling. The wood consumption for heating using a wood chips boiler, for instance, has been estimated equal to 100 MWh/y, or 125 m 3 /y, or 36 t/y.
Electric grid Electricity Control system Heating Figure 6. Scheme of the energy supply integration 7 CONCLUSIONS This case study represent an opportunity for the integration of the renewable energy in retrofit interventions. The results demonstrate the possibility of stimulating renewable penetration and socio-economical development of rural area with a low cost and low energy interventions. Energy conservation is possible because the envelope measures have been finalized to reduce the U-value and to adopt advanced technical solutions for energy saving in respect of heating, cooling and electricity supplies, whenever possible. Benefits of renewable energy systems have been evaluated according to the global energy analysis of the buildings and of the site. Renewable energy integration is possible because building will be equipped with a wind + biomass energy system. In order to fulfil different needs, feasible and smart controlled solutions have been provided. Actual wind on site data are needed. District generation and integration of renewable energy in the electric grid is not simple, but nowadays RE development makes it necessary to develop system control capabilities and strategies that have features equivalent to conventional power plants. Research has to be carried out to develop tools and investigate and verify technical solutions for including RE power plants as active components of the power supply system. For the case study here presented, the integration of wind power has been supposed respecting the Italian regulations. REFERENCES F. Butera (1995). Architettua e Ambiente, Etaslibri, Milano. F. Butera, P. Caputo (2004). Mérite - Baglio energeticamente sufficiente, Milano. CESI, Università degli studi di Genova (2002). Atlante Eolico Nazionale, Milano (cd rom). http://www.windpower.org.